Always wondered about this... Of the popular handgun ammos listed below, I'm taking a shot at ranking them from most 'powerful' to least. (by 'powerful' I mean biggest felt-recoil and/or hardest thump on the target - a fairly subjective rating, granted) Let me know if/where you think I'm off.
(let's assume typical, uniform bullet type and 'average' grain)

.44 Mag
.357 Mag
.45 ACP
.40 S&W
.357 Sig (never shot it - no idea about this one)
9mm
.38 Special
.380
.32

- Aaron